Standard Model Phenomenolgy.

Keith Hamilton's research concerns the development of high precision Monte Carlo simulations of collider Physics processes. These facilitate discovery and interpretation of new physics at the Large Hadron Collider (LHC). While precision simulations may not be needed to claim a discovery, e.g. if new physics appears as a clear `bump' in a smooth distribution, (as did the Higgs boson), in many scenarios, such as supersymmetry, signals are expected to manifest as subtle distortions in the shapes of distributions. An accurate understanding of the Standard Model background, subject to all experimental cuts, is then unavoidable for claiming a discovery, or setting exclusion limits. Precision simulations are also essential to determine what it is that has been found. The recently discovered 125 GeV mass Higgs boson is the prime example of this. In 2012-2013 Hamilton and collaborators in Milan and Oxford developed the world's most accurate simulation of Higgs boson production. This simulation is now used by default by the ATLAS and CMS collaborations, appearing in their publications confronted with measurements to probe Higgs boson properties. In recent years Hamilton's work has shown how to extend the methodology behind that cutting-edge simulation to an important wider range of LHC reactions. In the coming years Hamilton will work as part of a new team, comprising three other world-class researchers, to extend the most central, parton shower, component of general purpose Monte Carlo event generators -- the most widely used theoretical tools in particle physics. General purpose event generators are at the heart of the way in which collider physics is carried out, impacting on the whole community.

Thorne's work is complementary to that of Hamilton. It involves the precise details of the initial state appearing in hadronic particle collisions. At hadron colliders, e.g. the Large Hadron Collider (LHC), the particle beam is effectively made up of the fundamental particles inside the proton - quarks and gluons, generically known as partons. Predictions for Standard Model processes, and potentially those of new physics, require the precise partonic composition of the hadrons in terms of both the energy scale of the scattering process (e.g., the mass of a particle produced) and the momentum fraction of the incoming proton carried by the parton. Thorne is the lead member of an established PDF group that provides one of sets of parton distribution functions (PDFs) used as standard by both the experimental and theoretical analyses at the LHC and other high energy particle physics experiments. The approach is continually refined, both in terms of theoretical sophistication, and by inclusion of data which become available and due to increased precision or different sensitivity to PDFs, lead to further PDF constraints. Thorne's work will lead to improved PDF determination, providing updated PDFs for universal use, and he will also investigate the consequences of any changes. This will lead to a better understanding of current and upcoming measurements, and will also influence planning for future high energy particle physics experiments. Additionally, Thorne is a core member of the PDF4LHC working group (a member of the steering committee since the inception, and one of the main drivers and organisers) which provides recommendations for use of PDF sets at the LHC and acts as a direct liason to the LHC experimental community.

Both Hamilton and Thorne are involved in ever increasing precision for calculations at the LHC, which is particularly essential in order maximise the potential of the LHC, particularly given the current situation of no clear signals of new physics, but continual appearance of unprecedented variety and precision of Standard Model tests. Both will provide expertise in interpretingany deviations which could be the first sign of Beyond the Standard Model (BSM) Physics.

PDFs provide impact in a wide variety of areas. They are required for obtaining the best predictions and uncertainties of rates of particle production at any collider using protons. The UCL PDFs have been used to determine properties of the Higgs boson and in interpretation of precision electroweak measurements at the LHC, with these and similar activities continuing. PDFs also have a fundamental impact on decisions made concerning the energy at which colliders should be run, when breaks should be taken, and whether they should be continued or switched off. At present PDFs are particularly relevant for detailed planning of the high-luminosity phase of the LHC and for decisions regarding future colliders. PDFs are also required for the reaction rates for ultra-high energy neutrinos or other cosmic rays, and impact on the planning of detectors for these. As well as leading the MMHT PDF study, Thorne is a central member of the PDF4LHC committee, and the website which contains the recommendation used by numerous LHC studies, is based at UCL. The manner in which the proton is made up of quarks and gluons is a fundamental piece of knowledge of particle physics and the results of PDF analyses make their way into textbooks and popular science literature as a standard result. The study of PDFs requires theory, computing, modelling and comparison to a large amount of data from various experimental sources using advanced statistical techniques. Hence, it is excellent training for students and researchers for further academic study or many other workplace environments. The Centre for Doctoral Training in Data Intensive Science at UCL makes available courses and a group project for PhD students in particle physics. One student is currently involved in a project on image recognition coordinated by the Joint European Torus at Culham. Further interaction with the CDT will be investigated and encouraged. Recent students and postdocs have gone into the financial sector, data science in other fields and computing/cryptography.

As with the PDFs, besides their deployment in typical theoretical and experimental analyses, Monte Carlo event generators have an important role to play in the planning and design of future experiments, and in determining the way in which existing experiments are commissioned and run. Prominent documents on these subjects, such as the ATLAS technical design report and, more recently, CERN Yellow reports on the physics potential of the high-luminosity LHC, and FCC, are heavily comprised of simulation-based studies. The design and physics programs of current and future colliders will no doubt continue to be directly influenced by tools developed by Hamilton and colleagues, in particular, the Herwig++ and Powheg-Box packages. Owing to the remarkable prevalence of general purpose Monte Carlo event generators, in designing and interpreting collider physics analyses, and the importance of the key parton shower component inside them, forthcoming work of Hamilton and collaborators in the PanScales team can be expected to impact similarly. Research on precision Standard Model theoretical predictions is of fundamental interest in its own right, with Hamilton et al's recent innovations in the form of the MINLO and NNLOPS methods having subsections given to them in a new, high-profile, QCD textbook published by OUP.

Being fundamental research, the Standard Model phenomenology research fulfils the role of deepening and widening the field of human knowledge of the properties of nature, and is therefore of benefit to the general public. Such research is especially attractive to young people, and can serve as a gateway to enter a career in science, technology, engineering or mathematics, areas that are vital to the economy. This effect will occur indirectly, by disseminating the research results of the project to the wider public, as well as by training students who may choose careers outside fundamental research as outlined above.